No news is bad news

You know the story. You find a great candidate, they tell you how keen they are to join your company, you organise interviews and start the hiring process; the manager likes them so much they go out on a limb to get an offer to them... the candidate verbally accepts; and then... silence. You can't reach the candidate, they don't respond to your messages and the joining date is rapidly approaching

The exact circumstance can differ by varying aspects (permanent / contract / immediately available / four weeks notice / agency or corporate internal process etc) but at the end of everything - you receive no communication from the candidate.

My instinct is always that no news from the candidate at this point is bad news, regardless of how thorough or considered your process was.

How long do you normally wait before withdrawing your offer and moving on to other candidates?